Conventionally, in an image forming device, an image is formed with images of a plurality of colors being superposed by an optical scanning device (laser scanning unit: LSU), and therefore a problem that is referred to as color deviation sometimes occurs.
For example, image forming devices having configurations such as the following are known. A light beam such as a laser is scanned on the surfaces of a plurality of latent image carriers (also referred to as drum-shaped photoreceptor units or photoreceptor drums, for example) that correspond to each color of yellow, magenta, and cyan, and respective latent images are thereby written to each latent image carrier. Those latent images are then developed for images of each color to be formed on each latent image carrier, the images of each color are transferred from each latent image carrier to an image carrier (transfer belt), and the images of each color are superposed and formed on the image carrier. In addition, the images of each color are transferred from the image carrier to a printing sheet for an image to be formed on the printing sheet. In an image forming device of this kind of configuration, the images of each color sometimes deviate when transferred from each latent image carrier to the image carrier, color deviation occurs, and image quality deteriorates.
In particular, when an image forming device is being driven, the temperature inside the casing of the image forming device rises, the casing of the optical scanning device thermally expands, and as a result the positions of optical components such as Fθ second lenses fluctuate and color deviation sometimes occurs.
To prevent this kind of color deviation caused by thermal expansion, conventionally, a method is known in which a temperature sensor such as a thermistor is provided inside the optical scanning device, and color deviation is corrected according to the temperature inside and peripheral to the optical scanning device (see PTL 1, for example).
According to this method, the positions of the images of each color are corrected by controlling the latent image writing timing with reference to a table indicating characteristics of the color deviation amounts for each color for the image carrier with respect to temperature changes in the temperature inside and peripheral to the optical scanning device.